1914: Russian Navy Seized Codebooks
SMS Magdeburg ("His Majesty's Ship Magdeburg")[a] was a lead ship of the Magdeburg class of light cruisers in the German Kaiserliche Marine (Imperial Navy). While steaming off the Estonian coast, she ran aground off the island of Odensholm and could not be freed. A pair of Russian cruisers appeared and seized the ship. Fifteen crew members were killed in the brief engagement. The Germans destroyed the forward section of the ship, but could not complete her destruction before the Russians reached the ship. The Russians recovered three intact German code books and the current encryption key. They passed one of the code books to the British. The ability to decrypt German wireless signals provided the British with the ability to ambush German units on several occasions during the war, including the Battle of Jutland.